In the manufacturing of chemical compounds and substances, including the pharmaceuticals industry, solid materials are routinely transferred from storage containers, such as drums and bags, into vessels where the materials undergo processing, such as mechanical mixing and chemical reactions under a variety of conditions. The manual conveyance of such solid materials from containers into process vessels is generally referred as charging.
The charging process exposes the interior space of process vessels to oxygen-rich outside environments. The increase of the concentration of oxygen in a process vessel, mixed with flammable chemical matter emitting dust and vapors, poses a risk of fire or explosions. Process vessels may be equipped with mechanical equipment for purging the interior space of the process vessel, referring to the addition of an inert gas—most commonly nitrogen—to lower the oxygen concentration of the interior space and render it non-ignitable.
Conversely, the charging process also exposes the outside environment to dust and vapors are emitted from the process vessel. In the process of conveying solid materials into the vessel, dust and vapors may also be sent airborne while chemical matter is evacuated from containers and falls into the vessel. This may, in turn, lower the oxygen concentration outside of the vessel, particularly in the vicinity of the opening of the vessel, thus posing a risk to human operators working closely to the opening.